1. Field of the Invention
The present invention relates to sheet-conveying devices (post-fixation conveying devices) that are used in electrophotographic image-forming apparatuses such as copiers, printers, facsimiles, and multifunction machines having functions of the foregoing apparatuses, and to image-forming apparatuses including such sheet-conveying devices. In particular, the present invention relates to a sheet-conveying device (post-fixation conveying device) that cools sheets of paper that have had an image fixed thereto and to image-forming apparatuses including the sheet-conveying device.
2. Description of the Related Art
In general, fixation of an image to a sheet is performed at a high temperature. After the process, the temperature of the surface of the sheet remains high. While the surface temperature of the sheet is high, toner on the sheet does not completely harden and remains sticky. If image formation is successively repeated in such a state, the result is a plurality of sheets that are successively discharged and stacked onto a tray having high surface temperatures. If the toner on the sheets was not sufficiently cooled, the stacked sheets may adhere to each other due to the stickiness of the toner. Such a phenomenon is called blocking. Other potential issues may occur while the sheet is fed after fixation including feeding issues, such as jams.
Therefore, various techniques has been proposed to solve these problems. For example, an apparatus is known wherein a blower duct is provided on the downstream side in the sheet feeding direction so that the sheet is cooled immediately after fixation. The blower duct sucks in outside air using a fan and blows the air through an opening facing the sheet, whereby the sheet is cooled. The air, after it cools the sheet, flows in the sheet feeding direction together with the sheet, and is discharged to the outside.
In the above technique, however, the air that is fed from the blower duct is heated due to the high temperature of the sheet, and produces an airflow in the same direction as the sheet is being fed. This results in a hot airflow. Since the sheet is fed in this hot airflow, the sheets may not be sufficiently cooled.
To avoid such a problem, an apparatus is known wherein a sheet-cooling device that cools a sheet fed from a fixing device has a duct opening that faces the sheet from one side in the sheet width direction (a direction orthogonal to the sheet feeding direction). Cooling air is fed in the sheet width direction through the duct opening. In addition, a suction device is provided across the sheet from the sheet-cooling device. The suction device receives the cooling air that is blown from the sheet-cooling device. With such a configuration, cooling air is fed from the sheet-cooling device toward a heated sheet, in the sheet width direction, whereby the sheet is cooled. Meanwhile, the suction device removes the hot air around the sheet.
In the above technique, however, since the air is blown in the sheet width direction from the duct opening, there may be a difference in the cooling effect between an area near the duct opening and an area remote from the duct opening. That is, the sheet may not be uniformly cooled. Furthermore, blowing the air from one side in the sheet width direction and removing the air from the other side may cause the sheet to float. Moreover, since the flow rate of the air varies with the position in the sheet width direction, air turbulence may occur. This air turbulence tends to cause the sheet to float, resulting in jams in the sheet conveyance path.